Lumberyard VS Un-Real 4

So… This is the main question I have for this, which is better for me? I am a tiny bit familiar with lumber-yard, and none at all with Un-real 4, now I don’t want to here that lumberyard doesn’t have much documentation, I don’t care about that, what I need to know is, does un-real have FULL source code like lumberyard does to where I can edit how the engine works, am I able to make large maps such as 1k square mile maps (1000 sqaure mile maps) is it laggier than lumberyard, does it use native C++ code. How good would it be to create a game such as Arma with there gun/bullet physics , or have the escape from takorov cusimization, how easy is it to create UI, and AI? what premade tools does it already include?

Thanks, Cheers.

Are you expecting a link to the UE4 documentation? Because that’s the logical answer to so many broad questions.

Also, if you’re starting out then it’s best not to try and make a really huge game.